Recovery of the constituents of gaseous mixtures



Nov. 21, 1950 w. DENNIS 2,530,602

RECOVERY OF THE CONSTITUENTS 0F GASEQUS MIXTURES Filad Dec. 12, 1946 INVENTOR fl olcaff 20/1174;

BY 62; 8a... lu 6M ATTORNEYS Patented Nov. 21,

RECOVERY OF THE CONSTITUENTS OF GASEOUS MIXTURES Wolcott Dennis, Darien, Conn., assignor to Air Reduction Company, Incorporated, New York, N. Y., a corporation of New York Application December 12, 1946, Serial No. 715,864

'1 Claims.

This invention relates to the separation of the constituents of gaseous mixtures by liquefaction and rectification and particularly to the recovery of valuableconstituents of gases from the synthesis of ammonia and similar operations in which, as a result of repeated cycling of mixtures including rare gases of the atmosphere, such gases are concentrated and therefore available in substantial proportions.

Thus, for example, in the gases which leave the ammonia condenser after contact in the synthesis bomb with a catalyst to produce ammonia, there is a mixture consisting principally of hydrogen and nitrogen containing often as much as 20% of argon, some methane, and a small proportion of ammonia. Argon is a valuable product which is present in such gases in much greater proportion than in the atmosphere. The nitrogen and hydrogen are also available for reuse in the ammonia process and elimination of methane from such gases is desirable.

It is the object of the present invention to provide an effective and economically practicable method of treating gaseous mixtures of the type described to recover the constituents, thereby affording a supply of argon in greater quantities than have been available heretofore.

A further object of the invention is the provision of a useful method of removing undesirable constituents from the gases in the ammonia synthesis cycle, thereby improving the synthesis and coincidentally recovering the constituents as valuable byproducts of the operation.

Other objects and advantages of\the invention will be apparent as it is better understood by reference to the following specification and the accompanying drawing, which illustrates diagrammatically an apparatus suitable for the practice of the invention. Elements well known in the art have been omitted from the drawing for the purpose of clarity.

Since as indicated the gaseous mixture may contain small amounts of ammonia, it is desirable first to treat the gases for the removal of this constituent. This may be accomplished in any convenient way, as for example contact of the mixture with sulphuric acid. A scrubber (not shown) of any suitable construction may be used for this purpose.

The gaseous mixture, freed from ammonia, is in accordance with the present invention first compressed to a suitable pressure, for example in the neighborhood of 16-18 atmospheres in a compressor 3, and cooled in the usual intercoolers Q. It is then introduced through a pipe 5 to an of the exchanger H.

exchanger t which, as diagrammatically shown, includes chambers I, l and 9. It will be understood that any suitable form of exchanger may be employed. After passing through the chamber l in heat exchange relation with outgoing products, the gaseous mixture passes through a pipe ill to an exchanger II which is similarly shown as comprising chambers l2, l3, l4 and Iii. Here, the gaseous mixture is further cooled by heat exchange with products of the separation and is delivered through a pipe. It to a column I! having a compartment It at its lower end, which is operated at the initial pressure of the gaseous mixture. The compartment l8 includes trays I! having the usual caps 20. The gaseous mixture travels upwardly through the trays and into the tubes 2| which are immersed in liquid argon, a product of the separation in the column ll.

Partial liquefaction of the gaseous mixture occurs, the liquid falling back upon the trays l9 and accumulating in the bottom of the compartment It. This liquid contains the more readily condensible constituents of the gaseous mixture together with some of the nitrogen and hydrogen. The major portion of the nitrogen and hydrogen escapes from the tubes 2! to a pipe 22 and is delivered thereby to the chamber [3 After passing through the chamber, the mixture of nitrogen and hydrogen which ,is still at the initial pressure is delivered by a pipe 23 to an expansion engine 24 where it is expanded with external work and thereby further cooled. From the expansion engine 26 the mixture of nitrogen and hydrogen is delivered through a pipe 25 to the chamber it of the exchanger H and passes therethrough to a pipe 26 which delivers it to the chamber f the exchanger 6. Thence the nitrogen and hydrogen mixture escapes through a pipe Z'l and may be delivered to any suitable gasometer or other device for further use.

The liquid from the chamber it is delivered through a pipe 28 and pressure reducing valve 29 to an auxiliary column 30 having trays 3i and caps 32. The'liquid flows downwardly over the trays 3| and vapors arising therefrom are washed with reflux nitrogen supplied as hereinafter described. As a result, the liquid methane accumulates beneath the trays 3| and is vaporized by heat exchange with gases passing through the tubes 33 of a condenser. escapes through a pipe 34 controlled by a valve 35 and is delivered to the compartment I5 01 the exchanger H. Thence it travels through a pipe The vaporized methane I 38 to the compartment 9 of the exchanger 8 and is withdrawn through a pipe Bl. it may be stored in a suitable container tor subsequent use.

The eifluent from the column 3d consists of argon and nitrogen with small amounts of hy= drogen and escapes through a pipe 58 to an in-= termediate level of the column it which is provided with trays 39 and caps at. The eflluent passes upwardly through the upper trays of the column i] in contact with reflux nitrogen liquid. supplied as hereinafter described. As result oi rectification in the column ill, liqui argon accumulates around the'tubes 28 as hereinbelore noted.

The emuent from the column ll consists principally of nitrogen with small amounts of hydro gen and argon. It is withdrawn through a pipe li and passes through chamber 32 of an exchanger a3, thence through a pipe it to chamber 35 of an exchanger t and through a pipe 5'5 to a compressor it. Here the efiiuent is compressed from the pressure of the columns ll and 38, that is approximately 1 atmosphere, to a pressure of approximately 20 atmospheres or more, and is olelivered through a pipe 49 to the chamber 5E3 oi the exchanger d6, thence through a pipe 53 and valve 52 to a compartment at the bottom of the column 36. The efduent passes upwardly through the tubes 33, and the nitrogen and any argon are condensed, leaving hydrogen which is withdrawn through pipe E i and valve to the compartment 58 at the bottom of the column 21']. Thence it passes through the tubes 2!] and joins the nitrogen and hydrogen mixture which is sliminated in the tubes.

The liquid nitrogen accumulating in the charm ber 53 is withdrawn through a pipe 56 and delivered through a pipe 511' to the compartment or the exchanger Thence it passes through a pipe 5d and valve to the top of the column ll. afiording the reflux nitrogen liquid required for the maintenance of the separation in that colunin. The liquid nitrogen overflows through a tube 66 into a collector 62. A portion of the liquid nitrogen overflows from the collector 62 into the lower trays of the column 1' The remainder passes through a pipe and valve 66 into the top of the column 353, afiording the liquid nitrogen ef luent required for the separation therein. desired, a portion of the liquid nitrogen from the pipe can be delivered through a valve 55 and pipe 66 into the compartment it at the bottone or" the column ll to afford reflux liquid on the trays l9.

liquid argon which is one of the principal products of the separation is delivered from the column ll through a pipe 617 and a liquid pump to a pipe 89 which is connected to a compartinent ill of the exchanger =35. Thus, the nitrogen circulating through the exchanger 36 is cooled by the liquid argon which is vaporized and escapes through a pipe it to any suitable receptacle in which it may be stored. Argon in the vapor phase may be withdrawn, if desired, by connecting the pipe tl above the liquid level, in which case the pump 68 may be omitted. AS the result of the separation, nitrogen and hydrogen are available for re-use. Methane is eliminated from the mixture and may be used or discarded, and the argon which is concentrated in the gaseous mixture is recovered as a valuable production of the operation.

Various changes may be made in the details of procedure and in the apparatus as described without departing from the invention or sacrificing the advantages thereof.

I claim:

1. The method of recovering the constituents of gaseous mixtures including principally nitro= gen and hydrogen with a substantial proportion of argon which comprises compressing and thereafter cooling the gaseous mixture by heat exchange with separated nitrogen and hydrogen before and after expansion thereof, subjecting the mixture to partial condensation by heat ex= change with the liquid argon product of the oper= ation and thereby separating the major part of the nitrogen and hydrogen in the gaseous phase from a liquid enriched in constituents less vola= tile than nitrogen including argon, subjecting the enriched liquid to rectification to separate argon with the residue of nitrogen and hydrogen a a gaseous'efiluent and rectifying the gaseous eiilu cut to recover the argon in the liquid phase.

2. The method of recovering the constituents of gaseous mixtures including principally nitro gen and hydrogen with a substantial proportion of argon which comprises compressing and thereafter cooling the gaseous mixture, subjecting the mixture to partial condensation by heat exchange with the liquid argon product of the operation and thereby separating the major part of the nitrogen and hydrogen in the gaseous phase from a Liquid enriched in constituents less volatile than nitrogen including argon, subjecting the enriched liquid to rectification to separate argon with the residue of nitrogen and hydrogen as a gaseous effluent, rectifying the gaseous efiluent to recover the argon in the liquid phase and compressing and thereafter liquefying the gaseous effiuent from the second rectification to aflord reflux liquid for both rectifications.

3. The method of recovering the constituents of gaseous mixtures including principally nitrogen and hydrogen with a substantial proportion of argon and some methane which comprises compressing and thereafter cooling the gaseous mixture, subjecting the mixture to partial condensation by heat exchange with the liquid argon product of the operation and thereby separating the major part of the nitrogen and hydrogen in the gaseous phase from a liquid enriched in constituents less volatile than nitrogen including argon, drogen before and after expansion to cool the incoming gaseous mixture, subjecting the liquid enriched in constituents less volatile than nitro-= gen to rectification to separate liquid methade from an ei'fluent consisting of the remainder of the constituents in the gaseous phase and recti= tying the gaseous effluent to recover the argon in the liquid phase.

4. The method of recovering the constituents of gaseous mixtures including principally nitrogen and hydrogen with a substantial proportion of argon and some methane which comprises compressing and thereafter cooling the gaseous mixture, subjecting the mixture to partial condensation by heat exchange with the liquid argon product of the operation and thereby separating the major part of the nitrogen and hydrogen in the gaseous phase from a liquid enriched in constituents less volatile than nitrogen including argon, subjecting the liquid enriched in constituents less volatile than nitrogen to rectification to separate liquid methane from an eiliuent consisting of the remainder of the constituents in the gaseous phase, rectifying the gaseous eflluent to recover the argon in the liquid phase and comutilizing the nitrogen and hyeilluent from the second rectification to afford reflux liquid for both rectifications.

6. The method of recovering the constituents of gaseous mixtures including principally nitrogen and hydrogen with a substantial proportion of argon and some methane which comprises compressing and thereafter cooling the gaseous mixture, subjecting the mixture to partial condensatlon by heat exchange with the liquid argon product of the operation and thereby separating the major part of the nitrogen and hydrogen in the gaseous phase from a liquid enriched in constituents less volatile than nitrogen including argon subjecting the liquid enriched in constituents less volatile than nitrogen to rectification to collect liquid methane from an efduent consisting of the remainder of the constituents in the gaseous phase, rectifying the gaseous effiuent to recover the argon in the liquid phase and compressing and thereafter liquefying the gaseous eflluent from the second rectification by heat exchange with the liquid methane to afford reflux liquid for both rectificatlons.

' 6. The method of recovering the constituents of gaseous mixtures including principally nitrogen and hydrogen with a substantial proportion of argon and some methane which comprises compressing and thereafter cooling the gaseous mixture, subjecting the mixture to partial condensatlon by heat exchange with the liquid argon product of the operation and thereby separating the major part of the nitrogen and hydrogen in he gaseous phase from a liquid enriched in constituents less volatile than nitrogen including argon, subjectingv the liquid enriched in constituents less volatile than nitrogen to rectification to separate liquid methane from an eilluent consisting of the remainder of the constituents in the gaseous phase, rectifying the gaseous eilluent to recover the argon in the liquid phase and compressing and thereafter liquefying the gaseous eiliuent from the second rectification by heat exchange successively with the liquid argon product and the liquid methane to afiord reflux liquid for both rectifications.

7. The method of recovering the constituents of gaseous mixtures including principally nitrogen and hydrogen with substantial proportions of argon and some methane which comprises compressing and cooling the mixture, subjecting the mixture to partial condensation by heat exchange with the liquid argon product of the operation and thereby separating the major portion of the nitrogen and hydrogen in the gaseous phase, and then subjecting the remainder of the mixture including argon to successive rectifications to separate the methaneand argon respectively, withdrawing and compressing the efiluent from the final rectification and subjecting it to partial condensation to provide liquid nitrogen reflux for the successive rectifications. WOLCO'I'I DENNIS.

REFERENCES CITED The following references are of record in the file of this patent:

Um'rnb s'rs'rns PATENTS Number Name Date 1,498,766 Van Nuys June 24, 1924 2,009,084 Gomonet July 23, 1935 2,040,107 Schlitt May 12, 1936 2,040,108 chlitt May 12, 1936 2,040,116 {Wilkinson et al. May 12, 1936 2,089,543 De Baufre Aug. 10, 1937 2,180,435 Schlitt Nov. 21, 1939 2,240,925 De Baufre May 6, 1941 2,316,056 De Baufre Apr. 6, 1943 2,337,474 Kornemanu Dec. 21, 1943 

1. THE METHOD OF RECOVERING THE CONSTITUENTS OF GASEOUS MIXTURES INCLUDING PRINCIPALLY NITROGEN AND HYDROGEN WITH A SUBSTANTIAL PROPORTION OF ARGON WHICH COMPRISES COMPRESSING AND THEREAFTER COOLING THE GASEOUS MIXTURE BY HEAT EXCHANGE WITH SEPARATED NITGROGEN AND HYDROGEN BEFORE AND AFTER EXPANSION THEREOF, SUBJECTING THE MIXTURE TO PARTIAL CONDENSATION BY HEAT EXCHANGE WITH THE LIQUID ARGAON PRODUCT OF THE OPERATION AND THEREBY SEPARATING THE MAJOR PART OF THE NITROGEN AND HYDROGEN IN THE GASEOUS PHASE FROM A LIQUID ENRICHED IN CONSTITUENTS LESS VOLATILE THAN NITROGEN INCLUDING ARGON, SUBJECTING THE ENRICHED LIQUID TO RECTIFICAITON TO SEPARATE ARGON WITH THE RESIDUE OF NITROGEN AND HYDROGEN AS A GASEOUS EFFLUENT AND RECTIFYING THE GASEOUS EFFLUENT TO RECOFER THE ARGON IN THE LIQUID PHASE. 